The Commissioning Instrument will be mounted at the DESI focal plane behind the DESI Corrector. Its focal surface will consist of five CCD sensors and 22 fiber-illuminated fiducials whose positions have been engineered to work effectively with Platemaker. The surface will then be enclosed in a tall steel cylinder. The entire Commissioning Instrument will have the same mass and mass distribution as DESI’s Focal Plane System to ensure realistic operations.

The focal surface of the Commissioning Instrument will have 5 CCD cameras and 22 illuminated fiducials.
A rendering of the fully assembled Commissioning Instrument.

The Commissioning Instrument is scheduled to be installed at the Mayall Telescope in August 2018 and to begin a two-month commissioning run in November 2018. It will then be removed to make way for the installation of the DESI Focal Plane System.